The present invention relates to fault detection in semiconductor devices and more particularly to a method and system for providing a temperature contour map of a semiconductor die in a flip-chip device, thereby providing a more accurate indication of the location of shorts in the semiconductor die.
Semiconductor devices typically include a semiconductor die mounted to a substrate. The die includes an active area in which circuitry is formed. The circuitry in the active area is electrically coupled to the substrate using connections at the surface of the active area.
After fabrication of the semiconductor device, detection of the existence and positions of faults, such as shorts, is often desirable. For example, conventional semiconductor dies are mounted on a substrate with the active area at the top and the bottom of the die in contact with the substrate. This combination is a conventional device. Leads electrically connect the circuits in the active area to the substrate. To detect faults causing hot spots in such a circuit, a liquid crystal is conventionally used. A thin layer of liquid crystal is poured over the circuits at the top of the die. When power is applied to the die, the liquid crystal changes phase over some hot spots in the circuits. Due to the phase change, the color of the liquid crystal changes over the hot spots. The centers of areas where the liquid crystal has changed color mark the locations of shorts in the circuit. Consequently, the position of shorts in the circuit can be detected.
Although conventional liquid crystal detection can be used for circuits in conventional devices, this method does not function for flip-chip devices. In order to make electrical connection between the semiconductor die and the substrate, flip-chip devices mount the semiconductor die such that the active area faces the substrate. Connections, such as solder balls, on the surface of the active area make electrical contact to the substrate. Because the die in a flip-chip device is mounted with the active area in contact with the substrate, the circuits are not readily accessible. In addition, the portion of the semiconductor die below the circuits is significantly thicker than the portion of the semiconductor die in which the circuits are formed. Consequently, applying the liquid crystal to the readily accessible back of the die will not detect faults causing hot spots within the active area of the semiconductor die.
Furthermore, the application of the liquid crystal to the surface may not provide an accurate indication of the location of faults within the semiconductor die. Heat from shorts may dissipate non-uniformly in different directions. Thus, the center of the area in which the liquid crystal has undergone a phase change may not mark the location of the short. The position of the short may, therefore, not be accurately determined.
Accordingly, what is needed is a system and method for accurately detecting the positions of faults within a flip-chip device. The present invention addresses such a need.
The present invention provides a system and method for detecting a location of a short in a flip-chip device. The flip-chip device includes a semiconductor die and a substrate. The semiconductor die has an active area including a surface. The semiconductor die also has a plurality of connections coupled with the surface of the active area. The method and system comprise supplying power to the semiconductor die and sensing a temperature at a plurality of locations while power is supplied to the semiconductor die. The temperature is sensed at the plurality of locations using at least one thermal couple. The plurality of locations is disposed between the plurality of connections.
According to the system and method disclosed herein, the present invention allows temperature contours in the semiconductor die and, therefore, the locations of shorts to be detected more rapidly. Consequently, the ability to accurately detect shorts is increased.